The present disclosure relates generally to systems, methods, and apparatuses for determining fretted positions and note onsets of a stringed musical instrument.
1. Field of the Invention
Musical instrument players have a history of utilizing technology to allow their instrument to generate or control additional sounds. Certain violins and wind instruments, for example, have been physically and/or electronically modified to allow them to act as ‘controllers’ and thereby interface to external sound generating devices such as musical synthesizers. More universally, keyboards have had switches added to each key to generate on/off signals for controlling sound generation hardware and software. These so-called MIDI keyboards are generally regarded as highly reliable musical controllers. The guitar, although widely used in all types of music, has yet to have a reliable and cost-effective synthesizer interface instrument available to them. This deficiency is due not only to the lack of these instruments accurately determining fretted notes but also due to the unacceptable performance in detection of certain types of plucks (‘note onset’).
2. Description of the Prior Art
There have been numerous guitar-to-synthesizer interfaces disclosed but few have had commercial success. This is due to cost and/or performance limitations that have prevented widespread acceptance.
For example, so called waveform extraction interfaces, such as the Roland Corporation's commercially available GR series of guitar controllers, analyze the guitar's vibrating strings to determine what note is being played on a particular string. Such products suffer from slow responses due to the time necessary to reliably determine the period of the waveform (especially on lower frequency strings). This method is also notorious for generating unexpected ‘chirps’, wrong notes, added notes, and missed notes unless users are unnaturally precise with their playing style.
Other products have replaced the guitar strings with an array of buttons, sensors, or ‘fake strings’ (for determining what note is being played) and/or have replaced the plucking area of the strings with touch sensitive pads, joysticks, or another set of ‘fake strings’ (to determine when a pluck occurs). Instrument cost and the departure from natural guitar playing have prevented such ‘virtual guitar’ products from becoming widely accepted.
Other products have incorporated ‘split frets’ into guitar-like instruments for stopped fret detection. Specifically, each of the frets (22 frets, for example) is divided physically and electrically into segments, one segment for each string. Then each of the 132 segments (6 strings times 22 frets) is scanned to determine where each string is pressed. This solves string-to-string crosstalk problem that would otherwise cause issues for such a simplistic approach. However, this approach is fraught with problems such as high cost, difficulties in manufacturing, fret segments falling out, mistaken fret identities when a user ‘bends’ one string into an adjacent segment.
Other patents, including U.S. Pat. No. 4,468,997 by this inventor (now expired), U.S. Pat. No. 4,702,141 by Bonnano (also expired), have taught how to sequentially drive electrical current through the guitar strings and (1) sense resultant voltages at fret-string junctions along the current-carrying string as a means to determine stopped fret positions (Bonnano) or, (2) to sense voltage drops along the current-carrying string between fret pairs to determine stopped fret positions (Young). These methods allowed use on specially modified guitars having factory strings and factory frets. However, such methods of sequentially driving large amounts of current down the guitar strings had a myriad of issues including heating of the strings, calibration complexities, inadvertent introduction of switching noise into electromagnetic pickups on the guitar, and corrosion caused by high currents flowing through the dissimilar metal at the string/fret contact points.
Other patents have included descriptions of envelope followers for use in pluck detection and level detection for use in so-called Note Off computations. However, these followers have historically used fast-charge/slow discharge capacitors in an attempt to follow the peak movements of the waveforms. Although these followers are effective in following envelopes as they rise in energy, they are sluggish in following waveforms that decay very quickly. This results in delays in turning off notes and disruptive changes of tones.